1. Field of the Invention
The present invention relates to an alarm mechanism of an alarm clock.
2. Description of the Prior Art
A conventional alarm mechanism is arranged as follows: cam grooves are formed in one of an hour hand wheel gear and an alarm wheel gear that are located coaxially with each other, and cam pawls are formed on the other. When reached at the alarm set time, the cam pawls are fitted into the cam grooves by means of a spring force of an urging spring, thereby closing an alarm switch to detect the set time of an alarm. An alarm hand is force-fit into the distal end of the pipe portion of the alarm wheel gear, and a hour hand is force-fit to the distal end of the pipe portion of the hour wheel gear.
In such an alarm mechanism, when installing the pointers, it has been necessary to fit the cam grooves and the cam pawls to each other by operating a hand rotating knob, respectively force-fit the alarm hand and the hour hand into the pipe portion of the alarm wheel gear and the pipe portion of the hour hand wheel gear in a predetermined positional relationship by maintaining that state, and subsequently further adjust the positional relationship between the alarm hand and the hour hand by effecting a hand rotating operation. Since this adjustment work involves, for instance, the refitting of the hour hand, the adjustment work is very complicated and consumes time, so that it has been a large hindrance to the assembly process of clocks under the present situation.
In U.S. Pat. No. 4,693,612, one of the present applicants has earlier proposed an alarm mechanism which is capable of facilitating and simplifying the adjustment work remarkably and whose alarm accuracy is high. In this earlier invention, the arrangement is such that the cam grooves are formed in one of two skirt portions which abut against the alarm hand and the hour hand, while the cam pawls are formed in the other, and the cam grooves and the cam pawls are fitted to each other when these members in the skirt portions are opposed to each other, thereby detecting the alarm time.
Even in this improved earlier invention, the alarm hand and the hour hand are both fitted into the respective pipe portions in their skirt portions, and the cam pawls slides on the surface of the skirt portion. Therefore, the force-fitting of the alarm hand-side skirt portion and the pipe portion, must be firmly effected so as not to be interlinked with the rotation of the hour hand. For this reason, there are drawbacks in that there is a possibility of a crack occurring in the skirt portion, and that the work of force-fitting the alarm hand is required. Thus there has still been room for improvement.